1. Field of the Invention
The present invention relates to a technique of printing one print job by distributing it to a plurality of printing apparatuses.
2. Description of the Related Art
There have conventionally been many cluster systems which execute distributed printing using a plurality of printers to advance the print completion timing. This is because the output speed of a printer has an upper limit, and the use of not one expensive high-speed printer but a plurality of low-cost printers sometimes results in low cost.
As for the unit of distribution, there is known a technique of sharing output of copies of a print job requiring printing by a plurality of copies between printers. There is also known a technique of sharing output of pages of a print job requiring one copy between printers.
The cluster system is configured using a dedicated cluster server which performs RIP (Raster Image Process) for print data and distributes image data having undergone RIP to a plurality of printers. Alternatively, the cluster system is configured by a master printer which performs RIP for print data received by the printer, and a slave printer which receives image data having undergone RIP from the master printer and outputs it.
In the use of a dedicated cluster server, a high-performance host computer can implement high-speed RIP. However, a large installation space for the number of printers and the cluster server is necessary. The traffic of transferring image data of all pages occurs on the network. The cluster server must have a high throughput at high cost.
As a configuration similar to the latter one, there is a technique of performing page interpretation by a master printer for received print data to generate display list data as intermediate data, and transferring the display list data to another printer (e.g., Japanese Patent Laid-Open No. 2004-288071). This configuration can simplify the process and achieve high-speed printing because a printer which receives display list data only converts it into image data. The page description language (PDL) widely used as print data is sometimes not of a page independent type, and is not suitable for a parallel process. To the contrary, display list data facilitates a parallel process and implements an efficient page-distributed cluster because pages do not depend on each other. Display list data is often smaller in data size than image data, reducing the data transfer traffic.
However, the time taken to convert display list data into image data, i.e., the time taken for RIP changes between pages. This is because the number of drawing objects and their complexity are greatly different between pages. Even if an N-page document is printed by distributing print data of N/2 pages to each of two printers, the timings when the respective printers complete the print process of N/2 pages do not coincide with each other. In many cases, the timing when printing is complete by a printer which prints display list data containing many pages with many drawing objects at high complexity is much slower than the timing by another printer.